PCNA is a nuclear protein associated with cell cycle and has a molecular weight of 36 kD, it is required for the synthesis of DNA in cell. This antibody can react with PCNA in all vertebrates and insects, and is expressed in S phase, G1 phase and early stage of G2 phase in proliferating cells in. As the main marker of cell proliferation index, it is used to the study of proliferation of malignant tumor cell and judge the malignant degree, which has certain significance for treatment and prognosis judgment of tumor.